Fluid balance

Question 1

What to do to assess fluid status:

Answer 1

• Clinical examination: thirst, skin turgor, mucous membranes, postural hypotension, postural tachycardia, tachycardia, hypotension, oliguria
• Don’t forget daily weighs as a useful short to medium term measure of hydration status
• Urine output - for adults: 0.5mls - 1ml/kg/hour, for children: 1ml/kg/hour
• Invasive measures: arterial line BP/MAP, pulmonary capillary wedge pressure, central venous pressure
• Blood tests: serum osmolarity, creatinine, haematocrit
• Urine osmolality
• Chest x-ray

Question 2

What to do for fluid maintenance?
How much fluid is required?
How much electrolytes are required?
How much glucose is required?

Answer 2

• An adult male with ideal body weight needs 25-30mls/kg/day of water per day
• 1mmol/kg/day of potassium, sodium, chloride per day
• 50-100g/day of glucose to prevent ketosis

Question 3

What is in normal saline?

Answer 3

Normal saline: 154mmol of sodium and 154 mmol of chloride

Question 4

What is in Hartmans?

Answer 4

Hartmans: 131mmol of Na, 111mmol of Cl, 29mmol lactate, 5mmol K, 4mmol Ca

Question 5

What are some examples of maintenance fluids apart from normal saline and hartmans?

Answer 5

• 3% dextrose and 1/3 normal saline
• 4% dextrose and 1/5 normal saline
• 5% dextrose and normal saline (paediatrics)

Question 6

What is the maintenance fluid used in paediatrics?

Answer 6

5% dextrose and normal saline (paediatrics)

Question 7

What are replacement fluids?

Answer 7

• Given in addition to maintenance
• IVF used are the same as for maintenance but need to consider specific electrolyte requirements
• K and Mg+ particularly important in fasting states combined with GIT losses
• If only replacing K+/Mg+/PO4 do so in mini bags!!

Question 8

What are resuscitation fluids/options?

Answer 8

• Principle is to replace estimated losses to maintain end-organ perfusion in a rapid manner
• Boluses of maintenance fluids
• Albumex 20 (200g/L)/Albumex (40g/L)
• Haemaccel (sulfated gelain)
• Blood products
• Beware elderly/paediatric patients

Question 9

In what clinical situations are replacement considered?

Answer 9

• Need to calculate losses
• Post-operative/haemorrhage
• Wounds – enterocutaneous fistula
• Drains
• Urine – high output states – diabetes insipidus, post- obstructive diuresis
• GIT losses – stomas, vomiting, diarrhoea, ileus
• Sepsis
• Burns

Question 10

Calculating the maintenance dose:

Answer 10

average healthy adult requires appraise 2.5L water/day
increased requirements with fever, sweating, GI losses (vomiting, diarrhoea, NG suction), adrenal insufficiency, hyperventilation and polyuric disease
4:2:1 rule to calculate maintenance requirements
4mL/kg/h first 10kg
2mL/kg/hr for remaining weight >20kg
Maintenance electrolytes
Sodium over 3mEq/kg/day
Potassium over 1 mEq/kg/day